From ba05b39d265bdd16913f7684600d9d41e2796745 Mon Sep 17 00:00:00 2001
From: Richard Fitzgerald <rf@opensource.cirrus.com>
Date: Fri, 16 Sep 2022 11:35:05 +0100
Subject: [PATCH] soundwire: cadence: Don't overwrite msg->buf during write commands
Git-commit: ba05b39d265bdd16913f7684600d9d41e2796745
Patch-mainline: v6.1-rc1
References: git-fixes

The buf passed in struct sdw_msg must only be written for a READ,
in that case the RDATA part of the response is the data value of the
register.

For a write command there is no RDATA, and buf should be assumed to
be const and unmodifable. The original caller should not expect its data
buffer to be corrupted by an sdw_nwrite().

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20220916103505.1562210-1-rf@opensource.cirrus.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/soundwire/cadence_master.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/soundwire/cadence_master.c b/drivers/soundwire/cadence_master.c
index be9cd47f31ec..3ef472049980 100644
--- a/drivers/soundwire/cadence_master.c
+++ b/drivers/soundwire/cadence_master.c
@@ -544,9 +544,12 @@ cdns_fill_msg_resp(struct sdw_cdns *cdns,
 		return SDW_CMD_IGNORED;
 	}
 
-	/* fill response */
-	for (i = 0; i < count; i++)
-		msg->buf[i + offset] = FIELD_GET(CDNS_MCP_RESP_RDATA, cdns->response_buf[i]);
+	if (msg->flags == SDW_MSG_FLAG_READ) {
+		/* fill response */
+		for (i = 0; i < count; i++)
+			msg->buf[i + offset] = FIELD_GET(CDNS_MCP_RESP_RDATA,
+							 cdns->response_buf[i]);
+	}
 
 	return SDW_CMD_OK;
 }
-- 
2.35.3